15 Replies Latest reply on Nov 28, 2007 3:17 PM by 1-9C36HC

Surface parameterization during lofts

John Reinhard Nov 26, 2007 7:50 PM

Attached is a picture of a surface loft with guide curves. Ofcourse the curvy spline and straight spline will have differentparameters, but I am curious as how SW determines the parameters ofthe created surface. Why do the isoparams slant downwardinstead of going straight across? I have tried many differentways, but it always ends up the same. The only thing thatseems to make a difference is to add another profile curve ( theshort direction in this example).

loftparams.jpg 46.6 KB

Surface parameterization during lofts

Charles Culp Nov 26, 2007 8:04 PM (in response to John Reinhard)

Right click on the surface, and select "show allconnectors". This should give you moreinformation.

*Edit: Actually, I take that back, because those lines go"across" the loft, not "with" the loft, theywon't tell you what you want to know.... You can force pointsby using sketches for guide curves (it looks like you are usingsurface edges), and creating splits in the line; although I don'tknow what benefit that would have. You could also use splitline on the surface to create the same points, but that's evenworse...
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Surface parameterization during lofts

Matt Lombard Nov 26, 2007 9:00 PM (in response to John Reinhard)

if you use a boundary surface you can use connectors in both directions
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Surface parameterization during lofts

John Reinhard Nov 26, 2007 10:16 PM (in response to John Reinhard)

I have tried this example using just sketches as well as thesurface edge. I have tried the straight guide curve as aspline and a line. I tried using the boundary surfaceas suggested, but the only parameterization controldifference I got was that I now have curve influence options in Dir1 and Dir 2. Even though it has nice features in showing themesh and combs, the result was the same. I am using 2007, soI do not know if 2008 has added options in the loft or boundarysurface features. Only if I add an extra profile in the shortdirection just below the lower bend in the wavy spline while tryingthe boundary surface, do I get the parameterization I mightexpect.

So I guess what I really want to know is, how SW isthinking when it tries to create these surfaces, what is SWthinking when it determines the parameters of the surface. IfI understood this better, then I could create bettercurves/construction geometry in preparation for the feature.

Thanks again.
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- Surface parameterization during lofts
  
  Matt Lombard Nov 26, 2007 11:27 PM (in response to John Reinhard)
  
  I don't think anyone can answer the question you are asking, but, if you try using connectors with the boundary surface, you'll be able to control the parameterization better. For example, if you have the two edges and a spline between them, you can set the connectors on the edges to say about .7 and on the sketch at about .5, and this will control the flow of the UV lines.
  
  See the attached avi.
  
  Mark B if you're looking in, remember what I said about connectors in Boundary causing crashes? This video is your proof. The last connector I added and tried to adjust cause SW to hang and eventually crash.
  
  boundary.zip 13.5 MB
  
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  - Surface parameterization during lofts
    
    Charles Culp Nov 27, 2007 1:24 AM (in response to Matt Lombard)
    
    John,
    
    Did you set tangency to face in the Dir2 with a boundary surface? I made the exact same shape you have created there just lastweek (it's a handle grip, with finger divots) . It behaved how Ithink you wanted it to, I will post a screen-shot in the morning,and maybe re-create it in another model after I look at matt'sexample..
    
    *Edit: Screenshot attached. It is surrounded bysurface-lofts. Also, the funky surfaces below are because Istarted with an imported model.
    
    BoundarySurface-Grip.png 180.8 KB
    
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      John Reinhard Nov 27, 2007 3:41 PM (in response to Charles Culp)
      
      Charles,
      
      I did set the tangencies. My problem was that I could not getthe add connectors option to appear until I clicked not on thesurface, but on the edge. Thanks again.
      
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        1-9C36HC Nov 27, 2007 4:02 PM (in response to John Reinhard)
        
        Matt and all,
        
        Attached is the model I used to try to reproduce Matt's problem. It looks like Matt's SW crashed after adding the third control point, after modifying the first two. Can you all try and let me know if you have similar crash?
        
        Thank you
        
        boundary-connector crash.zip 140.2 KB
        
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        Charles Culp Nov 27, 2007 5:07 PM (in response to 1-9C36HC)
        
        Wow. I am sitting at my machine with SW2007 (not '08), so Irecreated a part and ran into the same problem. It onlyaffected me if I set the two edge conditions to"curvature", tangent and default worked appropriately. After adding 4 connectors, I got the error shown.
        
        Boundary-Curvature-Crash.png 8.5 KB
        
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        Matt Lombard Nov 27, 2007 5:18 PM (in response to Charles Culp)
        
        Thanks Charles. This has been "bugging" me for a while.
        
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        John Reinhard Nov 27, 2007 6:40 PM (in response to Charles Culp)
        
        I tried the same thing in 2007 and instead of an error message mySW instance just hung. If I place two boundaries going indir2 at the open ends, then it seems to work fine. Again thisis with curvature set on the edges as Charles said.
        
        Thanks.
        
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        Surface parameterization during lofts
        
        1-9C36HC Nov 28, 2007 3:17 PM (in response to Charles Culp)
        
        SW2008 SP1 is available. Can you and Matt try my model on it (as well as yours) when you get it.
        
        thanks
        
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        Brian Cayer Nov 28, 2007 11:56 AM (in response to 1-9C36HC)
        
        Mark, I opened your file and suppressed your boundary surface then added another boundary surface using your guide curve sketch. I am not skilled at all in using surfaces so after a few tries I was able to add 4 connectors and adjust them with out any problems.
        
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    1-9C36HC Nov 27, 2007 11:01 AM (in response to Matt Lombard)
    
    Matt,
    
    I can not reproduce this. Can you send me your model so that I can try.
    
    Thanks
    
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      Matt Lombard Nov 27, 2007 1:17 PM (in response to 1-9C36HC)
      
      Mark,
      
      I would but I didn't save it, and it obviously crashed. I just started with a centerpoint arc extruded some distance as a surface, and then used the Boundary to span the gap.
      
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    John Reinhard Nov 27, 2007 3:38 PM (in response to Matt Lombard)
    
    Matt,
    
    Thanks for the video clip. It helped quite a bit.
    
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